This Program Project grant is designed to enhance our understanding of the basic mechanisms responsible for gastrointestinal (Gl) motility. Knowledge of mechanisms that generate normal motility patterns will help explain what goes awry in motility disorders and develop novel approaches to therapies. In this Program we are investigating smooth muscle cells, Interstitial cells of Cajal (ICC) and PDGFRa+ cells of Gl muscles, which through electrical coupling, form a syncytial tissue we refer to as the SIP syncytium. Cells of the SIP syncytium generate electrical pacemaker activity and provide what has been known as 'myogenic' regulation of motility. SIP cells also receive and transduce inputs from enteric motor neurons, so they are key participants in neural regulation of motility. We have developed techniques to isolate and purify each class of cell in the SIP syncytium, and we have performed deep sequencing of the gene transcripts in these cells. Hypotheses in this proposal were developed from this unprecedented knowledge of the cell-specific transcriptomes of SIP cells. Four projects will investigate questions regarding the mechanism of pacemaking and propagation of electrical slow waves, integration of excitatory responses by ICC and smooth muscle cells in generation of propulsive colonic contractions, bioactivity and targets of purines released and metabolites produced in colonic muscles, and the fate and recovery of ICC in patho-physiological conditions causing loss of ICC. Three Core laboratories will support these projects. Core A will provide informatics support and aide investigators with experimental planning and data management. Core B will provide transgenic animal, isolate and sort cells by fluorescence activated cell sorting, and support organ cultures. Core C will analyze expression of genes and proteins in cells and tissues. Experiments will utilize transgenic mice as model organisms to test novel hypotheses. Ideas developed in rodent studies will be tested on cells and muscles of non-human primates and human patients. The research team is highly synergistic and collaborative and has a long track record of productivity and innovative contributions to neurogastroenterology.